I used to collect juvenile Spiny Puffers, and often had more than a dozen at a time in my holding tank. They are a soft bodied fish, quite vulnerable to Crypt and other problems. Once they are stabilized, though, they do very well. It's best to start with a small one, under two inches. Bigger ones tend to swim up and down against the glass, in what seems to be a state of perpetual agita. Smaller ones also learn to eat pelleted food very easily.
My treatment for fish with signs of crypt was:
1. about 10 minutes in fresh water, carefully adjusted to match pH and temperature, followed by:
2. Isolation in a SW 20 gal tank treated with Cupramine, at the standard specified strength, about 0.5, for about 10-12 days. The tank had plastic plants and nothing else, and was dimly lighted. It was set up from scratch for each usage, though I might treat several fish at once. Frequent water changes, retesting and adjusting the Cu level, are critical. If there seemed to be bacterial issues (cloudy eyes, etc.), Seachem Neoplex worked well.
Water changes during medication are important, always making sure med levels are held constant. Cupramine is VERY different from other copper meds. I wouldn't use anything else. It's the gold standard, and is effective at even lower doses, down to about 0.3, for some light infestations.